BR112018004309B1 - recyclable plastic article - Google Patents

Abstract

METHODS AND COMPOSITIONS FOR DIRECT PRINTING WITH IMPROVED RECYCLABILITY. The disclosure relates to ink compositions for digital printing on an outer surface of a plastic article. The ink compositions comprise an ink removal promoting additive. In some aspects, the ink removal additive may facilitate separation or release of the image from the outer surface of the article when the image is exposed to a liquid solution at an elevated temperature. Also disclosed are recyclable plastic articles having an outer surface with an image printed thereon using the disclosed ink composition and methods for removing cured ink from a plastic container. This summary is intended as an examination tool for purposes of research in the specific art, and is not intended to be limiting of the present invention.

Description

DESCRIPTIVE REPORT REFERENCE TO RELATED REQUESTS

[0001] This Application claims priority from US Provisional Patent Application No. 14/846,032, filed September 4, 2015, which is a continuation in part of US Patent Application Ser. No. 14/528,324, filed October 30, 2014, which is a division of U.S. Patent Application Ser. No. 13/168,181, filed June 24, 2011 and now issued as US 8,876,979, which claims priority to US Provisional Patent Application No. 61/360,512, filed July 1, 2010, and is still a continuation in part of the US patent document Ser. No. 12/581,952, filed October 20, 2009, which claims priority from US Interim Application No. 61/106,860, filed October 20, 2008, all of the above are incorporated by reference as if fully set forth herein. .

TECHNICAL FIELD

[0002] The present invention generally relates to ink compositions for digital printing on external surfaces of plastic articles. The present invention also relates to plastic items with digital images printed thereon, including plastic containers with digital images having improved adhesion and/or recycling characteristics, as well as methods to facilitate their recycling.

FUNDAMENTALS

[0003] The plastic container industry continues to employ increasing amounts of recycling. Container manufacturers have recently begun to produce containers with digitally printed labels that are of sufficient definition and quality to compete with and potentially replace previous conventional labeling techniques. Examples of such printing techniques are described in US Pat. No. 7,625,059 and US Pat. No. 7,736,713, which are incorporated herein in their entirety by reference.

[0004] Possible challenges arise when introducing containers with digitally printed labels into conventional container recycling processes. Some challenges were mentioned and discussed in US patent document 12/581,952, which is also incorporated herein by reference in its entirety. There is a clear trend among container manufacturers, brand owners, end users and government entities to improve and increase plastic container recycling efforts. Consequently, it is desirable to provide industry-acceptable items that are sufficiently compatible with current infrastructure and recycling processes, or that offer sufficient incentives and/or volumes to effect industry change. At least initially, it would be desirable to provide digitally printed articles that are recyclable using current industry standard processes, that is, processes that generally include high temperature caustic washing and milling. As such, there is a desire for digitally printed plastic items, such as containers, that have digital images that adhere to the item without quality issues throughout its shelf life, but are more easily removable during plastic recycling processes.

SUMMARY

[0005] In an exemplary aspect, an ink composition for digital printing on a plastic article is disclosed. The ink composition generally comprises a base ink; an ink removal promoting additive; and a carrier capable of dissolving at least a portion of the paint removal additive. The removal promoting additive is configured or selected to cause at least a portion of the cured ink droplets to separate or loosen from the outer surface of a plastic article when a digitally printed image is exposed to a liquid base (e.g., base of water) at or about a predetermined elevated temperature. Such predetermined elevated temperatures may, without limitation, include those associated with conventional recycling processes.

[0006] In another aspect, a recyclable plastic article is disclosed which has an outer surface with a digital image printed thereon by cured ink drops. The ink drops comprise an ink composition as summarized above which includes a removal promoting additive. Also disclosed are embodiments of methods for removing said ink from a plastic container and methods for facilitating such recycling.

[0007] Additional advantages of the invention will be set forth, in part, in the description that follows, and, in part, will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and obtained by means of the elements and combinations particularly indicated in the appended Claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE FIGURES

[0008] Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0009] FIG. 1 generally illustrates a side view of a portion of a plastic container with an embodiment of a digital image printed thereon;

[0010] FIG. 2 is a general representation of a quality review table/matrix that can be used to assess the acceptability of an image printed on a plastic article.

DETAILED DESCRIPTION

[0011] In various aspects, reference will now be made in detail to embodiments of the present invention, examples of which are described herein and illustrated in the accompanying drawings. While the invention will be described in conjunction with the embodiments, it will be understood that it is not intended to limit the invention to those embodiments. Otherwise, the invention is intended to cover all alternatives, modifications and equivalents which may be included in the spirit and scope of the invention as defined by the appended Claims.

[0012] For general context, and without limitation, a portion of a surface 10 of a plastic article (e.g., a container) with an embodiment of a printed image 20 is generally illustrated in FIG. 1. The illustrated representation of image 20 includes a basecoat 30 which may be comprised of a plurality of basecoat ink 32, and may also include a secondarycoat 40 which may be comprised of a plurality of overcoat inkdrops. secondary 42.

[0013] The containers (which include bottles) associated with the present disclosure are comprised of a plastic material or resin (e.g., acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), polystyrene (PS), polyethylene (PE ) density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), etc.). Furthermore, the containers may be single-layer or multi-layer containers and may be formed using various conventional forming techniques including, without limitation, injection molding, blow molding, thermoforming, etc. In one embodiment, the outermost layer/surface may comprise a virgin plastic material. Although, it is noted that containers in accordance with the teachings of the disclosure may also include some percentage of recycled content, including a percentage of recycled content in the outer layer of the container.

[0014] In one embodiment, the article (e.g., container) may include a first coat, or base coat (e.g., base coat 30 shown in FIG. 1). The basecoat 30 may consist of a plurality of drops of base ink 32 which are printed (e.g. digitally printed, e.g. by an on-demand inkjet process) onto an outer surface of the article and subsequently cured. or allowed to heal. The ink may be UV curable ink which is curable by UV radiation which can be applied by various known means, including but not limited to UV or LED lamps. The ink droplets may be monomer-based and consist of an ink composition that serves to improve the application of the ink droplets (e.g. provides good processing characteristics for printing) and/or provides a visual characteristic (e.g. color or texture). For embodiments, the basecoat 30 may comprise white and/or colorless portions. In addition, with the ink drops described, i.e. those that are monomer based, curing can cause the ink drops to polymerize. As the inks that are employed are not solvent-based, the ink can be compounded so that during recycling processes the ink does not bleed into solutions and discard volatiles such as solvents. Note that the US Environmental Protection Agency (EPA) has enacted guidelines for solvents; however, the polymers are solid and do not stomp or release volatiles. That is, the ink separation as described herein may be mechanical in nature, as the ink is in a cured polymer state and can be physically removed (e.g., in the form of flakes or film) rather than to be included as part of a chemical dissolution.

[0015] As summarized above, the ink composition that makes up the ink drops includes a removal promoting additive. In some aspects, the "removal-promoting additive" comprises at least one hydrophilic component or acidic component. The hydrophilic components may comprise one or more compositional elements that exhibit hydrophilic (water-like) properties. The acidic components may comprise one or more compositional elements that exhibit acidic properties. For some embodiments, the removal promoting additive will comprise a combination of hydrophilic and acidic components, i.e., at least two removal promoting additives. For some ink drop compositions, a "dual" composition, in which the removal promoting additive comprises hydrophilic and acidic components, a lower weight percentage (to the total) may be used to provide results comparable to using the composition with only a single additive.

[0016] Such hydrophilic components may include hydrophilic monomers, hydrophilic oligomers and water-dispersible monomers that provide the desired functionality. Hydrophilic monomers are often characterized as having oxygen or nitrogen atoms, in addition to halogens, in the backbone structure. Such monomers are generally prone to attack by polar solvents such as water and ketones. Hydrophilic monomers also tend to have a lower resistance to thermal degradation. Consequently, the inclusion of one or more hydrophilic components in the associated ink drops may, at a later point (such as the post-use recycling point), improve the separation of the image (i.e., the cured ink drops) from the plastic structure. of the article. By way of example and without limitation, in a cured state, the hydrophilic portion of a polymer will typically absorb water. When this occurs, water can act as a plasticizer, increasing the mobility of the polymer chains. The increased mobility can soften the polymer, making it more susceptible to removal. As such, exposing a plastic article, such as a container, including an image composed of an ink composition with a removal-promoting additive (e.g., hydrophilic monomer) to a liquid solution (e.g., stirred water) in an elevated temperature position will soften the ink composition (ie the hydrophilic monomer) and separate the image from the plastic material. The elevated temperature may be predetermined and may be a temperature that is above the temperature that the article would normally encounter in normal use. Furthermore, to the extent desired, an adhesion separation threshold can be set such that softening removal and subsequent removal only occur at elevated temperatures (e.g. during a recycling process) and is substantially prevented during use. expected normal. Note that aliphatic urethane acrylates are a general class of hydrophilic monomers that generally absorb water and can potentially be used as a hydrophilic component. In addition, as long as they are suitably viscous (ie, not too viscous) for inkjet/fingerprint application, some hydrophilic oligomers can also be used as a hydrophilic component.

[0017] Without limitation, for some embodiments, the removal promoting additive may include hydrophilic monomers with a weight percentage of the total weight (i.e., associated paint and removal promoting additive) within the range of about 0 % to 20% by weight. For some embodiments, the weight percentage of the removal promoting additive will be within the range of about 0 to 10% of the total weight. Without limitation, an example of a hydrophilic monomer that can be used is methoxy polyethylene glycol monoacrylate (e.g. CD 553, available from Sartomer USA, LLC (Sartomer)).

[0018] Note that some water-dispersible monomers are also hydrophilic and appear to absorb water when cured. With such a composition, water can act as a plasticizer and soften the cured ink composition (e.g., a cured ink film on the surface of a container), facilitating removal of the ink film during recycling processing. With embodiments of the disclosure, the inclusion of an appropriate hydrophilic component in the ink composition can add a hydrophilic quality to the ink, while maintaining jet capability and adhesion of the ink to the article's substrate over the life of the article.

[0019] Acid components include acidic monomers that have a measurable acid value. Note that the measurable amount may be based on pH, acid weight percentage, or titrated value of an alkaline chemical (eg, mg KOH/g [milligrams of potassium hydroxide per gram of monomer]). Also, for example, in a cured state, the acidic portion of the polymer may be vulnerable to a caustic solution. A reaction between the acid functionality of the polymer chain and the alkalinity of the solution can produce a decrease in adhesion to the applied substrate, promoting the separation of the polymer. Without limitation, examples of acidic monomers that can be used include acid acrylate oligomer (eg, CN 147, available from Sartomer) and monofunctional acid ester (eg, CD 9050, available from Sartomer). For example, when a container involving an acidic component is brought into contact with a wash (e.g., a conventional type caustic wash), the associated bonds can be broken, promoting an intended separation of the printed image (ink drops) from the plastic. substrate.

[0020] In other aspects, the removal promoting additive is configured or otherwise selected according to its desired properties that can facilitate removal of a cured ink composition from the surface of a plastic article. For example, in one aspect, it is desirable for the removal promoting additive to exhibit relatively high solubility in the solvent and relatively high aqueous solubility in combination with a glass transition temperature lower than the temperature typically used in conventional recycling processes. To this end, in exemplary aspects, the removal promoting additive exhibits a glass transition temperature (Tg) that is less than about 130°C. This may include removal promoting additives that exhibit a glass transition temperature (Tg ) that is less than about 120°C, less than about 110°C, less than about 100°C, less than about 90°C, less than about 80°C, less than about 70°C , less than about 60°C, or even less than about 50°C. In a further aspect, the paint removal additive has a glass transition temperature (Tg) in the range of about 50°C to about of 130°C. In a still further aspect, the paint removal additive has a glass transition temperature (Tg) in the range of about 55°C to about 125°C, or from about 65°C to about 105°C, or from approximately 55°C to about 95°C. In a further aspect, the paint removal additive may have a temperature of trans vitreous ion (Tg) in any range derived from any of the above exemplary values.

[0021] As one of ordinary skill in the art will appreciate, the desired level of aqueous solubility can be characterized as a function of, for example, the acid number of the removal-promoting additive. The acid number can be expressed in terms of a titrated value of an alkaline chemical (eg, mg KOH/g [milligrams of potassium hydroxide per gram of scavenger additive]). In these respects, the removal promoting additive may exhibit an acid number in the range of about 100 mg KOH/gm to about 250 mg KOH/gm, including values of 110 mg KOH/gm, 120 mg KOH/gm , 130mg KOH/gm, 140mg KOH/gm, 150mg KOH/gm, 160mg KOH/gm, 170mg KOH/gm, 180mg KOH/gm, 190mg KOH/gm, 200mg KOH/gm, 210mg KOH/gm, 220mg KOH/gm, 230mg KOH/gm, and 240mg KOH/gm. In another aspect, the paint removal additive has an acid number in the range from about 150 mg KOH/gm to about 205 mg KOH/gm, including values of 175 mg KOH/gm, 185 mg KOH/gm and 195 mg KOH/gm. In yet another aspect, the paint removal additive may have an acid number in any range derived from any of the above exemplary values.

[0022] In other aspects, the removal promoting additive may exhibit a glass transition temperature (Tg) of less than about 100°C and an acid number in the range from about 100 mg KOH/gm to about 250 mg of KOH/gm. In yet another aspect, the paint removal additive may exhibit a glass transition temperature (Tg) in the range of about 50°C to about 90°C and an acid number in the range of about 150 mg KOH /gm to about 205 mg KOH/gm. In yet a further aspect, the paint removal additive may have a glass transition temperature (Tg) and an acid number in any range derived from any of the above exemplary values.

[0023] By selecting a removal promoting additive that exhibits a desired combination of aqueous solubility and glass transition temperature, it is possible to provide a curable ink that exhibits the desired adhesion, scratch resistance, and solvent resistance, while providing facilitates the ink removal process as a precursor to a recycling process. When subjected to a caustic aqueous environment at a temperature that exceeds the Tg of the removal-promoting additive, a softening of the additive can result, leading to a relatively cleaner separation of the cured ink layer from the surface of the plastic on which it has been printed. .

[0024] These removal promoting additives can be present in the paint compositions in an amount from about 1 to about 20 percent by weight of the paint composition. This may further include specific exemplified amounts of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 and 19 weight percent. In another aspect, the paint removal additive may be present in an amount of any range of amounts derived from any of the above exemplary values. For example, removal promoting additives can be present in paint compositions in an amount from about 5 to about 20 weight percent of the paint composition.

[0025] In an exemplary aspect, paint removal additives that exhibit the above combination of aqueous solubility and relatively low glass transition temperature include styrene and maleic anhydride resins. In yet a further aspect, the styrene and maleic anhydride resins can be a copolymer of copolymer of styrene and maleic anhydride. In yet a further aspect, the styrene maleic anhydride is esterified styrene maleic anhydride. Examples of non-limiting commercially available styrene and maleic anhydride resins that are suitable for use as a removal promoting additive are Total's Cray Valley SMA®3840 and SMA®1440F resins.

[0026] In other aspects, the ink composition comprising the ink drops also comprises a carrier capable of solubilizing and dissolving at least a portion of the ink removal promoting additive. The carrier can be monomer based or solvent based. Exemplary monomers that can be used as a carrier include the class of acrylic monomers. By way of example, suitable acrylic monomers may include 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,3-butylene glycol dimethacrylate, isobornyl acrylate or isodecyl methacrylate or a combination thereof. In some aspects, the acrylic monomer is selected from 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate and 1,3-butylene glycol dimethacrylate. As noted above, in aspects, the vehicle capable of solubilizing the removal promoting additive may be solvent based. Suitable solvents may, in some aspects, be aprotic solvents or aqueous solvents. Specific examples, but without limitation, suitable solvent vehicles include N-methyl-2-pyrrolidone (NMP) and acetone.

[0027] The carrier component may be present in the ink compositions in an amount of from about 1 to about 20 percent by weight of the ink composition. This may further include specific exemplified amounts of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 and 19 weight percent. In another aspect, the carrier may be present in an amount of any range of amounts derived from any of the above exemplary values. For example, the carrier may be present in the ink compositions in an amount from about 5 to about 15 percent by weight of the ink composition.

[0028] The base ink portion of the ink composition may be any conventionally curable ink, such as conventional UV-curable ink. The base ink may be present in the ink composition in an amount ranging from about 50 to about 85 weight percent of the ink composition, including exemplary weight percent values of 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83 and 84 weight percent. In yet another aspect, the base ink may be present in any range of amounts which is derived from any of the above exemplary values. For example, the base ink can be present in the ink compositions in an amount of from about 65 to about 85 percent by weight of the ink composition.

[0029] In an exemplary aspect, described herein is an ink composition, comprising: (a) from about 65 to about 85 percent by weight of the base ink; (b) from about 5 to about 20 weight percent of the paint removal additive having a glass transition temperature of less than about 100°C; and (c) from about 5 to about 15 weight percent of the carrier capable of dissolving at least a portion of the paint removal additive. In accordance with this exemplary aspect, the base paint can be a UV white base paint, the paint removal additive can be styrene maleic anhydride resin, and the carrier can be solvent-based and can comprise N-methyl-2 -pyrrolidone (NMP) or acetone or other acceptable solvent.

[0030] As described herein, recyclable plastic articles are described which comprise the digitally printed image printed directly onto the curved outer surface, the image comprising cured drops of an ink composition as described above. In a further aspect, an exemplary recyclable plastic article comprises a curved outer surface with a digitally printed image printed directly onto the curved outer surface, the image comprising cured ink drops and the ink drops comprising a composition including an ink removal - promoting an additive having a glass transition temperature of less than about 100°C. In a still further aspect, the digital printed image has an adhesion index of at least 6.0 and up to 9.0 and the removal promoting additive is configured to causing the cured ink droplets to separate or detach from the curved outer surface of the when the digitally printed image is exposed to the basic solution at an elevated temperature of at least about 70°C.

[0031] In another aspect, the article comprises a plastic container. Even more, the plastic container is a bottle. In a further aspect, the plastic container is composed of one or more of the following materials: polyethylene, polyethylene terephthalate, high density polyethylene and polypropylene.

[0032] In another aspect, the removal promoting additive present in the ink composition is configured to cause the cured ink droplets to separate or loosen from the curved outer surface of the article when the digital printed image is exposed to a liquid-based solution. , such as an aqueous or water-based solution, at a predetermined elevated temperature. For example, cured ink droplets may separate or loosen from the curved outer surface of the article when the digitally printed image is exposed to a basic solution with a pH of at least approximately 10, 11, 12 or 13 and an elevated temperature in the range of about 70 to 90°C. In a further aspect, the basic solution has a pH in the range of about 12-13. In accordance with the aspects, after exposure to the basic solution at elevated temperature for a sufficient period of time, at least about 90 weight percent of the cured ink droplets separate from the curved outer surface of the article. In yet another aspect, the digitally printed image includes a basecoat including a plurality of cured basecoat ink drops and a secondary layer including a plurality of cured secondarycoat ink drops, wherein the secondarycoat is applied to at least a portion of the basecoat.

[0033] By way of example, and without limitation, an embodiment of a polyethylene terephthalate (PET) container including UV-cured printed ink with a mixed removal promoting additive was subjected to ink removal testing. The mixed removal promoting additive from the tested containers included acidic monomers of the above type, i.e., acid acrylate oligomer and/or monofunctional acid ester. The containers can be subjected to a bath solution comprising a pH level of at least 9.0, which can aid in the removal of labels as is generally known in the art of recycling plastic containers, the solution being heated to approximately 85°. C. Several samples were exposed to such conditions for 12 minutes, and were rated on a scale of 0 to 5 as follows:

[0034] 0-No improvement in removal compared to the control sample

[0035] 1 - Minimal improvement observed, removal obtained only in some areas by abrasion with a metallic object

[0036] 2-Some improvement observed, the entire film could be removed by scratches with a metallic object

[0037] 3- Ink film was removed by scratches with a fingernail

[0038] 4-Ink Film was easily removable by simply wiping with a clean cloth

[0039] 5-Ink film dropped during wash test.

[0040] The test was intended, among other things, to identify solutions that provide a removal performance level of 4 or 5. However, a level of at least 4 is not necessarily a requirement and, for some applications, a level lower removal rate may also be acceptable. The test results indicated that the inclusion of the removal promoting additives (acids) mixed in the ink composition provided a significant improvement in the removal of cured ink from the plastic material (PET). Although both forms of acid additives exhibited an improvement in promoting paint removal, with the instant test setup, a slightly lower percentage of composition of the acid acrylic oligomer as opposed to the monofunctional acid ester (10% versus 15%, respectively), was used to get at least a level 4 removal level.

[0041] In embodiments, the ink composition may optionally include a hydrophobic component. That is, the ink composition may, for example, include hydrophilic and hydrophobic components. Hydrophobic components may include hydrophobic (does not absorb water) monomers. Hydrophobic properties are generally related to polarity. A number of hydrophobic monomers are characterized as having an organic backbone structure composed primarily of hydrogen and carbon; and therefore these monomers tend to be non-polar and offer resistance to polar solvents (such as water and alcohols) as well as acids and bases. For such two-component embodiments, the ink composition must strike a balance between hydrophilic and hydrophobic components (eg, hydrophilic monomers and hydrophobic monomers). Hydrophobic monomers can help keep ink droplets adhering to the article substrate, and hydrophilic monomers can help smooth (and even separate) when the image is exposed to a recycling bath/process (e.g. agitated water at a high temperature).

[0042] For an embodiment of a container with an image printed thereon, at least a first base coat 30 (which may include a hydrophilic component) may be applied to a surface of a container at a first time t1 and to a first temperature T1. The temperature T1 will be in the temperature range appropriate for the application of the associated basecoat. In one embodiment, the basecoat 30 may be curable (e.g., ultraviolet (UV) curable) and may further be cured prior to application of a secondary coating.

[0043] For some embodiments, a secondary coating 40 may comprise a plurality of drops of secondary coating ink 42 that are distributed over at least a portion of the base coat 30. In addition, if desired, additional layers of "secondary" coatings (e.g., a tertiary layer, etc.) can also be applied to the secondary coating 40. With embodiments of the disclosure, the secondary coating ink droplets 42 can also be comprised of an ink composition that includes a hydrophilic component.

[0044] A plurality of secondary coating ink drops 42 may collectively form part of an application pattern which, in turn, may form all or part of an image. Furthermore, as generally illustrated in FIG. 1 , portions of one or more adjacent secondary coating ink drops 42 may overlap or mix with each other. The secondary coating 40, and the constituent secondary coating ink drops 42, may comprise a variety of known colors, including, without limitation, primary print colors such as cyan, magenta, and yellow. Also, controlling the overlap or combinations of certain colors in certain areas can provide additional “process” colors. In addition, the secondary coating ink droplets 42 may be curable. For example, UV curable secondary coating ink droplets may comprise all or part of the intended image. When curing by radiation, the ink composition may include a photo initiator. It is further observed that the paint cured on a container surface can be realized mainly by two bonds, i.e. a polar bond between the paint polymer and the plastic, and a mechanical bond due to the plastic surface having an irregular surface at a microscopic level (eg microstructures). For a number of embodiments of the present disclosure, it is best to attack both links. For some applications, a hydrophilic component may work better in mechanical bonds, while an acidic component may work better in polar bonds. Depending on the application, the secondary coating ink droplets can vary in diameter, which can range, for example, from about 10 microns to about 200 microns. The secondary coating 40 may be applied to a surface 10 of a container for the second time t2 and at a second temperature T2, wherein the second temperature T2 at which the secondary coating 40 is applied is generally lower than the first temperature T1 at which the secondary coating 40 is applied. base coat 30 is applied.

[0045] In embodiments of the invention, the time between application of a base coat and application of a secondary coat (e.g., t2 minus t1) can be reduced - e.g. to as little as ten seconds or less. For some modalities, the application time differential will be within two to six seconds. Furthermore, in embodiments, the application temperature differential between the temperature at which basecoat 30 is applied and the temperature at which a secondary coating 40 is applied to a portion of basecoat 30, i.e., T1 minus T2, may be controlled to be equal to or less than about 10°F. For some embodiments, the application temperature differential will be within about 5°F to about 10°F. In addition, for some applications, it may be desirable to modify the temperatures associated with the application of the base coat 30 and the secondary coat 40 so that the respective application temperatures are closer together, i.e., so that the temperature difference between the applied coatings is reduced or minimized. This can be accomplished, for example, by (a) decreasing/decreasing T1, (b) increasing/increasing T2, or (c) a combination of (a) and (b). Such above-mentioned time and/or temperature control in relation to the basecoat and secondarycoat can provide better adhesion of the resulting printed image to the article.

[0046] Note that in addition to time and temperature, irradiance is a factor that can also affect the effective cure rate for a printed image. That is, with certain moments (eg t1 and T2) and temperatures (eg T1 and T2) there may be an associated Irradiation - ie ε1 and ε2. For example, in embodiments, a basecoat can be cured on ε1 irradiation, and an associated secondary coating can be cured on ε2 irradiation. Furthermore, in the modalities, the effective cure rate - which may be based on a combination of time, temperature and irradiance - irradiance can generally be given by the following equation: Irradiation (ε) = (dΦ/dA) where Φ = flux radiant (measured in watts) and A = area (cm 2 )

[0047] For example, without limitation, the irradiance range for some modalities will be between about 0.1 watts/cm2 and about 10.0 watts/cm2.

[0048] For some applications, such as where a curable ink (eg a UV curable or radiation curable ink) is used, the relevant coating or ink may be cured after each respective print station. For example, without limitation, one embodiment of a process may, at least in part, comprise: applying the base coat; curing stage; secondary coating application; and healing stage. Alternatively, also by way of example and without limitation, the process may, at least in part, comprise: applying the basecoat; curing stage; application of the base coat; curing stage; secondary coating application and curing step.

[0049] In addition, for embodiments of the invention, it may be desirable that the subsequent processing/production rate of containers/bottles substantially matches or matches the flow/processing rates of the associated printing machine(s).

[0050] In addition, it has been found that the quality of printed images can be, at least in part, controlled and/or improved through one or more of the following techniques:

[0051] (a) selection and/or calibration of ink sets;

[0052] (b) temperature control of the substrate (ie, container surface); and/or

[0053] (c) time control.

[0054] With respect to the selection and/or calibration of ink sets, this is accomplished, at least in part, by the selection and/or calibration of inks comprising the base and secondary coatings. It has been found that the inks used can be selected to provide the desired time and/or temperature characteristics, including relative to each other in combination. For example, selecting certain inks that have produced viscosities may exhibit or provide certain effects related to the desired temperature.

[0055] With regard to controlling the temperature of the substrate (ie, container surface), the temperature of a relevant portion of a sidewall (or other part of a container) can be treated or controlled to some extent. For example, a certain portion of the container may be pre-treated. Such pretreatment can be facilitated using various known techniques which may include, without limitation, flame, corona and plasma treatment. However, the invention is not limited to specific pretreatment techniques.

[0056] With regard to time control, the time associated with the movement of containers, for example, through a production machine, as well as the timing of base coat and/or secondary coat applications, can be controlled. It may be desirable for the subsequent processing/production rate of containers/bottles to substantially match or match the flow/processing rates of the associated printing machine(s).

[0057] The present disclosure may also include a system for evaluating or evaluating the "acceptability", such as commercial acceptability, of a container with a printed image, such as a digitally printed label. That is, for embodiments of the invention, the evaluation or evaluation system may provide an "adherence index". FIG. 2 generally represents a quality review table/matrix that can be used to assess or assess the acceptability of an image printed on a container. As generally shown, the Y axis can involve numbers associated with an overall pass or fail score. In the illustrated embodiment, numbers 1 to 5 indicate that the containers are not acceptable, while numbers 6 to 9 indicate that the associated containers are acceptable. It is important to note that while a score of at least 6 will "pass" as acceptable against the table/snapshot matrix, the invention is not limited to the specific table/matrix shown and alternatively more scores may be provided for and/or Approval scores can be increased or decreased as desired or needed. A plurality of tests - which may include various standard tests, including those mentioned above - are represented in the columns provided on the X axis. For example, without limitation, Test 1 may include a “Sutherland Rub Test”, Test 2 may comprise a “3M #610 Tape Test”, Test 3 may include a “Simulated Ship Test” and Test 4 may include a “3M # 810 Tape Test”. As generally shown in the table, various “pass-or-fail” designations may be represented on the table in connection with each observed test. With respect to several of the "standard" tests mentioned above, the tests may be modified, as appropriate, for use in connection with a printed image as opposed to a traditionally applied label. For example, with various “tape” tests, which may follow ASTM D 3359-08 standards, table/matrix associated tests may or may not involve cutting part of the image with a cutting tool before applying a tape. pressure sensitive. That is, in one embodiment, "Test 2" may involve a "modified" 3M #610 tape test, in that the portion of the image portion of a tested container cannot be cut transversely or otherwise separated. of the container. Furthermore, with the table shown in FIG. 2, an indication of a “pass”, with respect to tape tests directly practicing the modified ASTM standard (i.e. the test does not involve cross cutting/separation) would generally be represented by any portions removed no larger than 2.0 mm2 . With respect to tape tests that directly practice the ASTM standard, an indication of “passing” would generally be a “4B” or “5B” rating (in ASTM Rating FIG. 1 Adhesion Test Results Rating), or would involve less than 5% of the printed area removed.

[0058] In one embodiment, it is desirable to provide a container with a printed image (e.g., digitally printed image) that at least passes a modified 3M #610 tape test and yet is "recyclable". A digital image printed on a container is considered “recyclable” if it achieves a rating lower than the “4B” rating (ie, 5% more of the area is removed) employing a test tape standard #810 ASTM D 3359. A container with a digital image that passes Test 2 (modified 3M Tape Test #610) and Test 3 (Simulated Ship Test), but fails Test 4 (3M Tape Test #810), would achieve an adhesion index of 6 .0 or 7.0. Such a container with a printed image having an adhesion index of 6.0 or 7.0 is commercially suitable for shipment (i.e., passing a Simulated Ship Test) while providing an adhesion associated with the printed image that is sufficient for normal/intended use, but it is separable favorably for later recycling. Put another way, the adhesion associated with the configured digital image is strong enough for its intended use, but does not prevent separation during recycling.

[0059] With respect to this table/matrix, each test can be conducted on an appropriate (eg, statistically significant or representative) sample of recipients. After all tests are completed, the results can be tabulated and entered into the table/matrix, to provide an “adherence” score. The associated score results can then be correlated.

[0060] Among other things, the teaching of the present disclosure can provide improved recycling. Recycling inks printed on various articles effectively can provide a number of cost and efficiency benefits as well as providing benefits to the environment. For example, without limitation, containers with digitally printed images (which may be formed from UV-cured or cured ink) that are comprised, at least in part, of an ink composition that includes a hydrophilic and/or acidic component may be conveniently removed in connection with conventional plastic recycling processes. The industry standard recycling process for plastic containers conventionally includes grinding containers into granulated plastic flakes, subjecting these flakes to a high temperature caustic washing process, drying the clean flakes, sorting and extruding them into resin pellets for resale. With embodiments that incorporate aspects of the disclosed teachings, the digital image on the container may remain with the resin flakes after the milling process, the digital image will be substantially separated from the resin flakes during the high-heat caustic wash process, which may be stirred, and thus not contaminating the clean resin flakes to be formed into resin granules.

[0061] With separation techniques, there are at least four methodologies that can be employed - alone or in various combinations - to attack polar and/or mechanical bonds to promote ink removal from the article. Techniques include those using: (1) water-based or liquid solutions (for example, for additives with hydrophilic components or with the desired Tg and acid numbers as described herein); (2) caustic components (e.g., for additives with acidic components or the desired combination of Tg and acid number as described herein), and chemical reactions can be used to release polar bonds; (3) heat or temperature; and/or (4) mechanical force (eg, high pressure (psi) spray).; or any combination thereof.

[0062] The disclosure provides for a number of recycling processes that can be used to remove ink from the article. For example, one embodiment of a method for recycling plastic containers comprises: providing a plastic container with a digital image, the ink composition including a removal promoting additive (e.g., a hydrophilic or acidic component); and exposing the digital image to a liquid solution, for example water with or without a caustic component), at an elevated temperature; optionally stirring the solution. Before or after exposure, the container may be subjected to a grinding operation. Similar embodiments can be said along the lines of including dry milling, elutriate, washing, drying and elutriate.

[0063] Another process, which may be more similar to conventional, commercially available industrial recycling (eg from SOREMA (Italy)), may entail a single wash, wet mill, centrifuge, sorting and float/separation tank. A “single wash” can, for example, be employed with bottles transported (e.g. by an adjustment screw or multi-screw system) through a high pressure wash (e.g. a high temperature caustic wash). This can add a mechanical force component to aid in label removal. Usually bottles are whole, that is, not wetted before such washing. Materials, including polymerized inks, can be washed and dropped into a collection system or crate below the conveyor mechanism.

[0064] In another aspect, the present disclosure provides a method of removing cured ink from a plastic container, the method comprising: (a) providing a plastic container with a curved outer surface with a digital image printed directly onto the curved outer surface of the plastic container by an on-demand inkjet printing process, the image comprising cured ink drops applied directly to the curved outer surface of the plastic container and having an adhesion index of at least 6.0 and above through about 9.0 and the ink droplets comprising a composition including an ink removal additive having a glass transition temperature of less than about 100°C; (b) exposing at least a portion of the digitally printed image of the plastic container to a basic solution at an elevated temperature of at least about 70°C; and (c) removing at least a portion of the digital printed image from the curved outer surface on which the image has been printed.

[0065] In yet another aspect, the plastic container is a bottle. In yet another aspect, the plastic container is composed of one or more of the following materials: polyethylene, polyethylene terephthalate, high density polyethylene and polypropylene.

[0066] In a further aspect, the paint removal additive comprises a copolymer of styrene and maleic anhydride. In a still further aspect, the paint removal additive has a glass transition temperature (Tg) in the range of about 50°C to about 130°C. In yet a further aspect, the paint removal additive has a glass transition temperature (Tg) in the range of about 65°C to about 110°C. In still a further aspect, the paint removal promoting additive has a glass transition temperature (Tg) in the range of about 55°C. C to about 65°C. In an even greater aspect, the paint removal additive has an acid number in the range from about 150 mg KOH/gm to about 205 mg KOH/gm. In a still further aspect, the paint removal additive has an acid number in the range from about 165 mg KOH/gm to about 205 mg KOH/gm.

[0067] In a further aspect, the basic solution is an aqueous solution having a pH in the range of about 12-13 and wherein the elevated temperature is in the range of about 70 to 90°C. In yet another aspect, the step Removal includes scratching or cleaning the ink from the container after exposing the image to the basic solution. In a still further aspect, the paint is mechanically removed in the form of flakes or film.

[0068] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and various modifications and variations are possible in light of the above teaching. Embodiments have been chosen and described to explain the principles of the invention and its practical applications, so as to enable others skilled in the art to utilize the invention and various modalities with various modifications as appropriate to the specific use contemplated. The scope of the invention is intended to be defined by the appended Claims and their equivalents.

A. EXPERIMENTAL

[0069] The following examples are presented in order to provide those skilled in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and/or methods claimed herein are made and evaluated, and if are intended to be exemplary only and are not intended to limit disclosure. Efforts have been made to ensure accuracy with regard to numbers (eg amounts, temperature, etc.), but some errors and deviations must be accounted for. Unless otherwise noted, parts are parts by weight, temperature is in °C or room temperature, and pressure is atmospheric or near-atmospheric.

[0070] In the exemplary examples below, various ink compositions were prepared in accordance with the present disclosure and tested for use in direct printing onto an external surface of a plastic article. Ink compositions can be prepared by first dissolving the ink removal additive in the carrier and then adding the carrier solution to a base ink. The prepared ink composition can then be used for printing directly onto the outer surface of the plastic article.

[0071] The performance and recyclability of the various ink compositions on plastic articles were also evaluated. Ink compositions, including UV-curable ink having a removal-promoting additive and a carrier, were printed directly onto the surface of a polyethylene terephthalate (PET), polyethylene (PE) and/or high density polyethylene (HDPE) samples. and cured.

[0072] The cured ink from the sample was then subjected to ink removal tests, which may include tests of one or more of: adhesion, scratch resistance and solvent resistance properties. Samples may be subjected to various bath solutions which can aid in label removal, as is generally known in the art of recycling plastic containers, for example, a bath solution comprising a pH level of at least 9.0 and the solution being heated to approximately 75°C or 85°C. The test was performed at time periods including immediately after treatment (im) and 1 hour (1 hour) after treatment.

1. EXEMPLO 1.[0073] The materials shown in Table 1 were used to prepare the compositions described and evaluated in this document.

1. EXAMPLE 1.

NA * = remoção de tinta muito ótima para testar (toda tinta removida)[0074] For the following example, the additives promoting the removal of the tested samples were waxes and resins. The carrier was acetone or N-methyl-2-pyrrolidone (NMP) (commercially available from Sigma Aldrich). Ink formulations and performance data of the invention are provided in Tables 2-5 below. For the following data, “pass” indicates that no ink removal was observed and “fail” indicates that significant and/or complete ink removal was observed. Any % of value listed corresponds to the % of ink removal observed.

NA* = very optimal paint removal to test (all paint removed)

[0075] As the data shows, the SMA3840 and SMA1440F ink formulation samples showed improved performance. The SMA3840 ink formulation showed some sign of improvement, which indicates an improvement in ink removal when compared to the control. The SMA1440F ink formulation did not demonstrate any significant signals during normal use (“in use”) tests, but strong removal during the caustic wash test. The test was repeated several times on PET, EPET and PE, all showing good removal in the caustic test. 2. EXAMPLE 2.

[0076] For this example, ink compositions, including UV curable ink having a removal-promoting additive and a carrier, were printed directly onto the surface of a polyethylene terephthalate (PET), polyethylene () and/or polyethylene samples of high density (HDPE) and cured. The removal-promoting additive of the tested samples was copolymer of styrene and maleic anhydride (SMA1440F, commercially available from Cray Valley USA, LLC), and the carrier was N-methyl-2-pyrrolidone (NMP, commercially available from Sigma Aldrich). . Ink formulations and performance data are provided in Table 6 below.

[0077] As the data shows, about 100% removal of the ink compositions of the invention was observed compared to only 50-60% removal from the standard ink controls. In HDPE samples, the ink compositions of the invention exhibited greater than 50% ink removal compared to only approximately 10% ink removal for the standard ink controls. The results of the inventive ink compositions meet current recycling guidelines published by the Association of Post-Consumer Plastics Recyclers.

[0078] It will be apparent to those skilled in the art that various modifications and variations may be made to the present invention without departing from the spirit or scope of the invention. Other embodiments of the invention will be apparent to those skilled in the art from the specification and practice of the invention disclosed herein. The specification and examples are intended to be regarded as examples only, with a true scope of the spirit of the invention being indicated by the following Claims.

Claims (13)

1. Recyclable Plastic Article, characterized in that it comprises: a curved outer surface with a digitally printed image directly printed on the curved outer surface, the image comprising cured ink drops and the ink drops comprising a composition: from 65 to 85 percent by weight of a base paint; from 5 to 20 weight percent of an ink removal promoting additive having a glass transition temperature of less than 130°C; and from 5 to 15 weight percent of a carrier capable of dissolving at least a portion of the paint removal additive; wherein why the digitally printed image has an adhesion index of at least 6.0 and up to 9.0 and the removal promoting additive is configured to cause separation or release of cured ink droplets from the curved outer surface of the article when the digitally printed image is exposed to the basic solution at an elevated temperature of at least 70°C. 2. Recyclable plastic article according to Claim 1, characterized in that the article comprises a plastic container. 3. Recyclable plastic article according to Claim 2, characterized in that the plastic container is a bottle. A recyclable plastic article according to Claim 1, characterized in that the paint removal additive comprises a copolymer of styrene maleic anhydride. 5. Recyclable plastic article according to Claim 1, characterized in that the paint removal additive has a glass transition temperature (Tg) in the range of 50°C to 110°C. 6. A recyclable plastic article according to Claim 1, characterized in that the paint removal additive has a glass transition temperature (Tg) in the range of 55°C to 85°C. A recyclable plastic article according to Claim 1, characterized in that the paint removal additive has a glass transition temperature (Tg) in the range of 55°C to 65°C. A recyclable plastic article according to Claim 1, characterized in that the paint removal additive has an acid number in the range of 150 mg KOH/gm to 205 mg KOH/gm. A recyclable plastic article according to Claim 1, characterized in that the paint removal additive has an acid number in the range of 165 mg KOH/gm to 205 mg KOH/gm. 10. Recyclable plastic article according to Claim 1, characterized in that the article is composed of one or more of the following materials: polyethylene, polyethylene terephthalate, high density polyethylene and polypropylene. 11. Recyclable plastic article according to Claim 1, characterized in that the removal promoting additive is configured to cause the separation or release of cured ink drops from the curved outer surface of the article when the digitally printed image is exposed to a basic solution with a pH in the range of 12 to 13 at an elevated temperature in the range of 70 to 90°C. A recyclable plastic article according to Claim 11, characterized in that upon exposure to the basic solution at elevated temperature, at least 90 weight percent of the cured ink droplets separate from the curved outer surface of the article. A recyclable plastic article according to Claim 1, wherein the digitally printed image includes a basecoat that includes a plurality of basecoat cured ink drops and a secondary coat that includes a plurality of secondary ink drops cured coating, the secondary coating being applied to at least a part of the basecoat.